Field of the Invention
The present disclosure relates to image processing for forming an image having optical anisotropy.
Description of the Related Art
In recent years, development of technologies for controlling reflection characteristics of print images has been advanced. For example, there is an effort afoot to enhance design of a printed material by controlling glossiness distribution.
There is a technology for producing anisotropy of glossiness (angular dependence of glossiness) in a printed material. The anisotropy of glossiness is such a property that the appearance of a printed material is different depending on an observation direction. This technology is discussed in Yanxiang Lan, Yue Dong, Fabio Pellacini, Xin Tong, “Bi-Scale Appearance Fabrication”, ACM Transactions on Graphics (TOG)—SIGGRAPH 2013 Conference Proceedings TOG Homepage archive, Volume 32, Issue 4, July 2013 (hereinafter referred to as “Xin Tong”). In this technology, first, a shape (height) is formed using a 3D printer, and then the shape is colored using a color printer, so that an anisotropic bidirectional reflectance distribution function (BRDF) is produced in a printed material. In this Xin Tong, one pixel is divided into a plurality of micro-areas (5×5×2=50), and a surface shape (height information) and color material information of each micro-area are determined based on the BRDF.
In the technology discussed in Xin Tong, printer control parameters need to be determined in such a manner that the BRDF achieves desired characteristics for each micro-area, to produce the anisotropy of glossiness. Specifically, it is expected to perform such complicated processing that a BRDF of a printed material is estimated from control parameters of printer, and the control parameters are optimized to minimize a difference between the estimated BRDF and a desired BRDF. Since the control parameters need to be thus determined by optimization with iteration, the calculation time increases.